<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>DOM</title>
</head>
<body>
    <h1 id="title">111111</h1>
    <h1>222222</h1>
    <h1>333333</h1>

    <script>
        let h2 = document.querySelector("#title");
        h2.innerHTML = "444444";
    </script>
</body>
</html>